Thanks for the responses. The car has just about every bolt-on you can do. Long-tube headers, spin-tech mufflers, cold-air, throttle-body, plenum, underdrive pulleys, AC delete, Diabelo tuner. It's a stock block. Anyway. I'm running between 5000 and 6500 rpm for 30 minutes on track. A radiator upgrade is really whats needed. Since I recently replaced the stock radiator, I'm looking for a quick, cheap fix. When I've run other cars on the track the 19 psi cap has helped. I've found an aluminum reservoir that uses a standard cap. I might try that.